Household pets often are kept indoors and deposit their wastes in an absorbent composition, referred to as pet litter or cat litter. Half a century ago, indoor pets commonly used a box of sand to receive their wastes. Since then, pet litter has evolved into a specialty market, which began with the use of industrial absorbents. Today, a suitable base material for producing pet fitter is clay, which is inexpensive, absorbs liquids, and is easily disposed of, such as in the garden, or in the trash. Many clays are used as pet litters because of their excellent absorptive qualities. Among them, attapulgite clay, which is hydrous magnesium aluminum silicate, is one of the most commonly used pet litters. Similarly, fuller's earth is a combination of attapulgite clay and bentonite clay.
Bentonite, which is a montmorillonite clay, is formed of hydrous magnesium aluminum silicate and is widely used as pet litter. Its two common forms, sodium bentonite and calcium bentonite, are distinguished by having either sodium or calcium cations. Calcium bentonite, also known as southern bentonite, is an acid activatable clay that can be treated with hydrochloric acid or sulfuric acid to significantly increase its surface area and enhance it absorptive properties. It is the better absorbent of the two. Sodium bentonite has the ability to swell several times and forms gel-like masses in water, while calcium bentonite swells much less. Sodium bentonite also is known as Wyoming or western bentonite.
Two other common pet litters are kaolin, or china clay, and sedimentary opal clay mixtures. Kaolin is a hydrous aluminum silicate of the Kaolinite mineral group, having the formula Al.sub.2 O.sub.3.2SiO.sub.2.2H.sub.2 O. A commercial opal clay mixture contains sedimentary opal. Opal clay contains about 20 percent more silicon dioxide than is found in bentonite and has high porosity, which provides a high absorption capacity. Both clays are commonly sold as pet litter.
The process of producing a clay based pet fitter is similar with any type of clay material. Raw clay, which typically contains about 35 percent water, is mined from an open pit. Large earth movers deliver the clay to trucks, which haul it to a plant where it is dried in a kiln and crushed in several stages. During processing, different clays and other ingredients can be blended to produce a pet litter having special qualities, such as clumpability or odor control. After blending, the product granules are sorted by screening into various sizes. The final pet litter can be a mixture of sizes, which is more absorbent than when all granules are the same size.
The usefulness and performance of ordinary clay or other litter materials has been improved in three general areas. First, it has been discovered that litter is easier to keep clean if wet particles agglomerate or clump together, making it easier to remove the spent litter and waste products from the unspent litter. Second, several experimenters have added chemical or biological agents to litter in an attempt to digest the animal wastes or otherwise reduce odors. Along these same lines, litter can be scented to mask odor. Third, special litter materials have been developed that are especially absorbent. Several patents have issued in each of these areas.
The first type of patents disclose several techniques for clumping litter particles when wetted. For example, U.S. Pat. No. 5,216,980 to Kiebke combines granular clay with a gluten containing hydrophilic media. U.S. Pat. No. 5,183,010 to Raymond et al uses potato starch, gum, or polyvinyl alcohol to bind wet particles, plus boron to accelerate hardening. U.S. Pat. No. 5,152,250 to Loeb mixes granular litter with grain flour to cause agglomeration and mineral oil to cause the flour to adhere to the grains. U.S. Pat. No. 5,094,189 to Aylen et al adds potato starch to bentonite clay. U.S. Pat. No. 5,000,115 to Hughes mentions that certain natural bentonite clays, alone, are capable of clumping when wetted. U.S. Pat. No. 4,685,420 to Smart uses a polymer in clay to form a gelled agglomerate when wetted.
These and other methods of causing spent litter to clump offer an improvement over non-clumping litter. Because only wet litter forms clumps, the spent litter and the waste contained by it can be completely removed from the litter box, while permitting unused litter to remain behind. Thus, clumping litter is efficient and economical, allowing both solid and liquid waste to be removed from the litter box without requiring that the balance of clean litter also be removed. Further, clumps are easy to remove from a litter box, which makes the cleaning job much more pleasant and raises the expectation that this job will be done more frequently. Consequently, it is expected that clumping litter results in decreased waste odor in the home, due to the frequent and complete cleanings.
The second type of patents add a chemical agent that is intended to reduce odor. For example, U.S. Pat. No. 5,303,676 to Lawson combines bentonite with sodium bicarbonate or potassium bicarbonate coated with a mixture of mineral oil and siliceous material to deodorize the litter. ZnO can be added as a bactericide. U.S. Pat. No. 4,607,594 to Thacker combines bentonite with perlite, which has been treated with carbonate, bicarbonate or hydrogen phosphate. U.S. Pat. No. 4,517,919 to Benjamin et al adds undecylenic acid, a fungicide, to bentonite or other base material. U.S. Pat. No. 4,494,481 to Rodriguez et al uses transition metal salts in the litter box to control urine odor. U.S. Pat. No. 4,459,368 to Jaffee et al mixes calcium bentonite with calcium sulfate dihydrate to control odor. U.S. Pat. No. 4,437,429 to Goldstein et al uses zeolites to control odor in bentonite. U.S. Pat. No. 3,941,090 to Fry adds cedar bound with alfalfa. U.S. Pat. No. 3,916,83 1 to Fisher uses popcorn as litter, with added bactericides. U.S. Pat. No. 3,892,846 to Wortham uses A1, Zn, Sn, Ca or Mg salt of an hydroxamic acid in litter to resist odor by inhibiting bacterial decomposition of urea to ammonia when wetted by urine. U.S. Pat. No. 3,789,797 to Brewer et al combines bentonite and alfalfa, which supplies chlorophyll. U.S. Pat. No. 3,636,927 to Baum adds camphane compounds, which smell like cedar oil. U.S. Pat. No. 4,844,010 to Ducharme et al uses cyclodextrin in clay to absorb nitrogenous compounds. U.S. Pat. No. 4,704,989 to Rosenreid adds absorptive materials to clay litter, deodorizers and bactericides. U.S. Pat. No. 4,67 1,208 to Smith adds limestone to litter to neutralize urine and raise pH. U.S. Pat. No. 4,465,019 to Johnson adds dried citrus pulp to fitter. Japan Patent 3044-822 discloses an animal litter composed of clay and a water insoluble chemical deodorant, which may be an organic acid and its salt. Japan 3020-100 discloses use of bentonite, zeolite, or cristobalite plus deodorizer. EPO Publication 76,447 reduces ammonia content of air in animal stalls by lowering pH, through addition of a mixture of urea phosphate, phosphoric acid, sulfuric acid or alkali metal hydrogen sulphate and an organic acid. The low pH suppresses pathogenic bacteria by encouraging growth of acidophilic organisms such as lactobacilli, increasing lactic acid content. EPO Publication 39,522 manufactures litter from cellulosic fibers, pelletized, with added fungicides and bactericides.
These chemical agents may achieve success, although it appears that some could be expensive and others might require large concentrations to effectively treat any significant volume of animal wastes. Some of the chemicals might cause environmental problems, especially if allowed to build up by disposal in a dump site or garden over a long period of time. For this reason, alone, the use of deodorizers, bactericides, fungicides, acids, metal salts, and perhaps other similar materials appears to be a poor choice. In addition, pets walk through the litter box. Thus, these chemicals will be in contact with the pet's feet for substantial periods of time, which might cause irritation or other health problems. As pets groom themselves, the chemicals may in ingested. Further, the pet may track these chemicals through all areas of the house, spreading potential problems to human inhabitants, as well.
A few patents have attempted to use biologic agents to reduce odors. For example, U.S. Pat. No. 5,154,594 to Gamlen combines clay with digestive bacteria to break down the waste. Japan Patent 2154-629 combines multiple types of bacteria on a sawdust growth medium to break down ammonia, which is a bacterial decomposition product and major odor component, and other excrement and thereby prevent odor. Japan Patent 1085-125 discloses the combination of sawdust and thermophilic bacteria on the floor of a cattle shed to control odor. The mixture is placed in a compost shed for several weeks to produce mature compost. Soviet Union 1,091,889 discloses an animal bedding made of composted manure. Thermophilic bacteria in the manure cause an increased temperature that kills disease microorganisms. After composting, the manure is reused as bedding. Denmark Patent 86,908 combines cellulose and coccidium-retarding agent plus a protein rich material. These biologic agent patents seem unlikely to be completely successful, since composting or digesting wastes produces odors.
The third type of patent, in which absorbency is increased, is represented by United States Patent No. 4,557,881 to Crampton, which makes highly absorptive cat litter from clay fines that are compacted and then broken into larger particles. Absorbency is increased by adding an antideposition agent, which might include Wyoming bentonite, which is known to form a gel when wetted. The content of United States Patent No. 4,591,581 to Crampton is similar. Improving absorbency would be expected to make a litter more efficient, since liquid wastes might be captured in the granular material rather than being allowed to pool at the bottom of the litter box.
These many approaches to improved handling of animal wastes demonstrate that controlling odor of animal wastes is long standing problem. Some of the approaches deal with specialized problems that are unlikely to be reproduced with home litter boxes. For example, those treatments directed to cattle barns are dealing with cellulose based wastes, since cattle are herbivores. In contrast, home pets like dogs and cats consume a modify protein diet and their wastes tend to be far more putrid. Those techniques that claim to digest wastes are unlikely to be a full household cure, since the digestion process itself produces ammonia, which is a source of strong obnoxious odor from wastes. Thus, it appears a household litter that is odor free or at least can delay significant odor formation for a substantial time period is yet to be developed.
It would be desirable to have a litter or a treatment for litter that prevents formation of odor causing substances. Digestive schemes alone are unlikely to prevent odor, since digestion produces odor if only for a short time.
Further, it would be desirable to have a litter that can prevent formation of obnoxious odor without requiring an added fragrance to mask various odors that ordinarily develop. The addition of a fragrance to litter, for the purpose of covering bad odors, often is not a satisfactory solution since the odor continues to exist in the background of the fragrance. Of course, animal wastes have an immediate odor that a mild fragrance might cover. It is subsequently developed odors, such as ammonia, that tend to be most obnoxious and permeating. These are the odors that are most important to prevent.
Similarly, it would be desirable to have a litter or a treatment for litter that prevents formation of odors for at least a full day and preferably longer. Even the most attentive pet owner can be delayed from promptly emptying a used litter box. Ordinarily, the odors from a used fitter box become obnoxious quite soon after the use and soon can permeate a house. Therefore, if these odors are substantially eliminated for one or two days, or more, the ambience of the house is greatly improved.
Moreover, it would be desirable to combine an odor free litter or treatment for litter with a clumping litter, both to simplify emptying the spent portion of litter from the litter box and to maintain the waste in contact with the treated litter for effective odor prevention.
Another desirable goal is to control or suppress odor while using only a small amount of active agent. The chemical or biological treatments known in the prior art might involve prohibitive expense. Further, it would be undesirable to add significant quantities of any sort of agent to established litters such that they might change the character of the litter material, resulting in the agent being tracked about the house on the pet's feet.
To achieve the foregoing and other objects and in accordance with the purpose of the present invention, as embodied and broadly described herein, the product and method of this invention may comprise the following.